Electronic wave chopping circuits



Sept. 16, 1952 J. w. GRATIAN ELECTRONIC WAVE CHOPPING CIRCUITS 4 Sheets-Sheet l Filed March l0, 1950 N @SM QN/Il N Nwk.

4 Sheets-Sheet 2 J. W. GRATIAN ELECTRONIC WAVE CHOPPING .CIRCUITS Sept. 16, 1952 Filed March lO, 1950 mslm rllll Sept 16 1952 J. w. GRA-HAN 2,611,084

ELECTRONIC WAVE CHOPPING CIRCUITS Filed March l0, 1950 4 Sheets-Sheet 5 J. W. GRATIAN ELECTRONIC WAVE-CHOPPING CIRCUITS 4 Sheets-Sheet 4 Fil'ed March 10, 1950 @w mwN... @w Mmmm IlElEIN .jljlljl 5&5,

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IN V EN TOR.

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Patented Sept. 16, 19.52

Joseph W. Gratian, Rochester, N. Y., assigner to Stromberg-Carlson Company, a corporation of New York The present invention relates to electronic circuits and, more particularly, to electronic circuits suitable for selecting, or choppingout, .a desired vportion of a continuous periodic electric wave. which selected portion may then be utilizedlin any vdesired manner. While the invention is of general utility, it is particularly suitable for use in 'investigating the frequency'r and. transientresponse of electrical apparatus, especially in connection with magnetic recording equipment arranged to translate relatively low frequency phenomena. In many instances it is desirable to separate, or chop out. a, portion lof a continuous periodic wave and to utilize theV chopped out portion to investigate the response thereto of'various kinds of electrical equipment. Such a situation is found, for example, in apparatus arranged to amplify and translate a speech wave train which has been modified by multiplexing equipment or secrecy equipment in such a manner that certain portions of the'wave trainareomitted. It is then'necessary to ascertain the response of such apparatus. to `simulated signals such as chopped or garbled speech. Again, the choppedoutporftion of the wave may be utilized to investigate the transient response of amplifying equipment arranged to .amplifya continuous sinusoidal wave and wherein it is necessary to examine the jbehavior of equipment when subjected to 1a single cycle `of the sinusoidal wave and 'to'v ascertain Athe effect of the equipment upon the relatively Vabrupt end portions of the selected cycle.

It is desirable in'testing arrangements of the above-described type to `provide a wave selecting or chopping circuit which may select asingle cycle of a continuous sinusoidalwave, alternate cycles thereof, or every nthcycle of the period wave. present invention to provide' anew and improved electronic wave chopping circuit lof versatile character which is suitable for use in testing the vresponse characteristics .of electrical equipment.

It isa further-object of the invention to provide -a new and improved electronic .wave chopping the base line of `the test signal substantiallyundisturbed'between the selected cycles.

Accordingly, itis the primary object yof the '-It `is still another .gram of Fig. 1;

Application March 1o, 195o,V seriarNo. 148,927

2i claims; (c1. 25o-'27) object of the invention .to provideV a new yand improved electronic wave chopping circuit `adaptedgtc be. energized by. a

continuous periodic wave and arranged to provide a, test signalcomprising a single cycle, successive alternatev cycles, or every nth cycle of said period wave and wherein means are provided for reducing transients occurring at the end portions of said selected cycles to `permit examination of the effect of apparatus suppliedwiththe test signal uponsaid end portions.

The invention, both-as to its organization and method-of operation, together with further objects and advantages thereof,` will best be understood byreference to4 the following specification ytaken in connection with the accompanying drawingsin which; l p" Fig. l is a schematic diagram in'block'di'agram vform of anvelectronic wave chopping circuit embodying the principles? of my invention; Fig. 2 is a scherriatic diagram 'of the block dia- Figl y3 is ,a schematic diagram of an'alternative embodiment ofaportion ofthe circuit of Fig. 2:

and .l t

Figs 4 (a) 4 (d) are Atiming diagrams illustrate ing wave forms vwhich occur `in certain portions of the circuit of Fig.,2.

f Referring n'ow to the drawings there is illus-l trated in Fig. 1, in block diagram form, an electronic Wave chopping circuit J constructed in accordance withtheprinciples' of my invention. The telectrical wave, a portion of which is to be separated, or vchopped out, for'test purposes, is

illustrated asthe continuous sinusoidal wave l0 which is connected through a selector switch indicated generally atill to an input amplifier l2. The output of theinput amplifier 'is' connected to a scuaring circuit I3jtov the output of which ,are connected in cascade' relation in the order named l adiiferentiating circuit l 4, a gating pulse trigger circuit i5, a balanced clipper and amplifier i6 and a -balanced gate circuit Il. `The output of the Yinput amplifier l2 is also connected through a lead I8 to an input circuit of the balancedjgate circuit [1.'v Auxiliary signals suitable for-testing the electrical equipment may 'be introduced at input terminal -I`9 to another input section of the'balanced'gate circuit I1. The koutput of the balanced -gate Y,circuit I1-is selectively connectedby means 'ofthe switch ril toma finalamplifier and filter 2G, the output of which supplies 'a suitable test signal tothe apparatus under examination. ',For'exampleYV thegtest signal maycoinprise a vsubstantially#undisturbed Vbase line 2i on which 'is'fsuperimposed a single 3 selected cycle 22 of the continuous sinusoidal input Wave I0.

To condition the gating pulse trigger circuit I5 for control by the continuous input wave, there is provided a biasing trigger circuit 23, the cutput f which is connected to the gating pulse trigger circuit by means of lead 24. A feed back connection from the gating pulse trigger circuit I to the biasing trigger circuit 23 is made through a selector switch 25. The biasing trigger circuit 23 may be initiated manually by a starting circuit 26 which is connected to the biasing trigger circuit 23 through a selector switch 21. Alternatively, operation of the biasing trigger circuitmay be initiated at a variable frequency rate by means of a variable frequency oscillator 28 which is operated at a frequency lower than that of the incoming wave I0 and is connected to the biasing trigger circuit through a selector switch 29. The signal output of the input amplifier I2 is connected to the variableV frequency oscillator. 28 through a lead 30 so as to synchronize the operation of this oscillator with the incoming continuous wave. i

Referring brieiiy to the operation of the above described electronic Wave chopping system as a whole, the continuous input wave I0 is supplied to the input amplifier wherein it, is amplified to a sufficient degree to provide proper operation for the squaring circuit I3; The squaring circuit I3 is utilized to derive from the continuous input wave lll a rectangular shaped wave having the same frequency as the input wave and having relatively steep sloped sides. Differentiation of the output of the squaring circuit in dilferentiator I4 produces control pulses, alternate ones of which are of opposite polarity, these control pulses corresponding in time to the leading and trailing edges of the rectangular wave produced at the output terminals of the squaring circuit I3. The gating pulse trigger circuit I5 is of the general type referred to as a flip-flopcircuit in which a pair of 'electron discharge Vdevices are arranged to be switched abruptly from a conductive to a non-conductive state, or vice versa, in response to a rst one of the control pulses from the differentiator I4 and to be returned to ,their original state by the next succeeding control pulse of the same polarity. There is thus produced at the output terminals of the gating pulse trigger circuit I5 positive and negative going gating pulses'the. duration of which corresponds in time to a single cycle of the input wave, I0. The oppositelysensed gating pulses produced in the output circuit of the gating pulse. circuit I5 are supplied to theclipper and amplifier VIii wherein the leading and trailing edges ofthe gating pulses are substantially sharpened, The gating pulses are then supplied to the balanced gate circuit I1 wherein they are utilized to switch on ,one section of the gate circuit while simultaneously switching off the other section thereof so .that each section is switchedon and off in accordance with the gating pulses. The input wave I0 is supplied to one section of the gate Vcircuit and the sections of the gatingl circuit are so ad',- justed that no portion o f the gating pulsesappears in the output circuit of the gating circuit I 1 and only that portion of the continuousinput wave I0 which occurs between the leading and trailing edges of the gating pulses appears in the output of the 4balanced gate circuit. I1. The output of the gate circuit I1 is applied to the final amplifier and filter .20 wherein switching transients which occur during the leading and trailing edge intervals of the gating pulses are removed by filtering action and the selected cycle of the input wave amplified to suitable proportions for use in testing the particular electrical equipment.

The selector switch II is utilized to supply either the test Asignal comprising selected portions of the input Wave, or the inputl wave itself, to the final amplifier and hence to the equipment under test. By such an arrangement, a comparison can be made of the response of the equipment under test to the continuous input wave and to the chopped out portions thereof. In addition, the selector switch II, when connected to supply the input wave directly to the final amplifier and filter 2U, provides a ready means for. checking the frequency response of the particular section of the filter employed, as will be more readily apparent from a consideration of the filter circuit in more detail hereinafter. A

In the arrangement described thus far, it has been assumed that the gating pulse trigger circuit is turned on and off by successive control pulses from the diiferentiator I4 so that every other 'cycle of the input wave I0 is passed by the balanced gate circuit I1 to the final amplifier and filter 20. However, in order to select a single cycle of the input wave, the biasing trigger circuit 23 is arranged to control thel bias voltage supplied to the gating pulse trigger c ircuit I5 so as normally to disable the circuit I5 and to prevent actuation'thereof by the control pulses from the differentiator-I4. The biasing trigger circuit is arranged tobe turned on by the manual start circuit 26 or by the variable frequency oscillator 28 so that the bias voltage to. the gating pulse trigger circuit ischanged to permit actuation thereof by the' next succeeding control pulse. The bias trigger circuit is turned off by means of a feed back connection from the gating pulsetrigger circuit I5 to the bias ,trigger circuit, the bias trigger circuit remaining fin the off condition until subsequent enerization thereof by either of the sources 26 or 28.

Withsuch an arrangement a wide variety of test signals may be obtained from the incorning wave. For example, with the selector switch 25 closed, closure of the switch 21 causes the biasing ,trigger circuit 23` to supply enabling bias to the gating pulse trigger circuit, the control pulse immediately following, closure of the switch 21 turning on the gating pulse generating trigger circuit and the next succeeding control pulse turning off the circuit I5. Turning off the cir-'- cuit I5 also produces a feed back pulse for turning off the biasing trigger circuit. There is thus .produced in the output of the final amplifier a single cycle of the input wave I 0. y Y

. In the' event that alternate cycles of the input wave are to be supplied to the equipment under test, the switch 25 is opened and upon closure of' switch 21 the gating pulse trigger circuit I5 `continues to be turned on and off at a frequency equal to one-half that of the input wave so that alternate cycles ofthe incoming wave are selected for testl purposes. j'

If several cycles are to be omitted, for example, `if every fifth cycle is to'be selected, the switch zimay be opened and switches 25 and 29 cicsed so that the biasing trigger circuit is turned on at 'the repetition rate of the variable frequency oscillator 28. The biasing trigger circuit is again turned off after each pair of active control pulses -in'iamanner similar to that described in connection with'the single cycleoperation. Inrl'considering specific embodiments of thecircuits indicated in block diagram' form in Figli,v

lt-l-irou'ghanlnput potentiometer 46 to ground pot'entiah*4 The arm of the potentiometer 43 is connected 'to the controlelectrode 44 of an electron discharge device 45. In order to providelinear amplification of the input wave I6 in the device 5,*there is provided an unby-passed cathode fresister 46 which is-connected between the cathode ofthe device i5 and ground. The amplified input wave, which appears at the anode of the device 45, is coupled to the input circuit of' the s'quaring circuit i3 through a coupling capacitor 50.

In order to determine that suicient voltage is produced in the anode circuit of the device l5 to operate the squaring circuit, means'are provided for indicating the amplitude of voltage appearing at the anode of device 45. In the illustrated embodiment this indicator arrangement comprises -resistors lll, $6, which are connected in series between the anode of device 45 and ground, and a neon tube 49 which is connected across the lowermost resistor 58'. The values of resistors lil and 48 are so chosen that the neon vtube 46 will conduct Whenthe'voltage at the anode ofrdevice :45 exceeds'the minimum requirements ofthe squaring circuit |3'. Thus, by adjustment of the potentiometer i3 the proper voltage level for the squar- 'ing circuit may be provided.'

The squaring circuit |3 may comprise vany suitable circuit arrangement for deriving a rectangular shaped Wave froml the continuous'sinusoidal input Wave. However,` to provide `a rectangular Wave having relatively ste-ep sloped sides, I pre'- ier to employa circuit commonly known as' a Schmitt trigger circuit, which is capable' of producing a relatively steep sided rectangular wave when excited by the amplified sinusoidal input volta-ge. As illustrated, this squaring circuit comprises a pair of electron discharger devices 5|, 52 the cathodes of which arev connected through a common cathode resistor 53 to ground potential.

r'l2-hev anode oi the device 5| is connected through a coupling network comprising a parallel connected capacitor 54 and resistor 55 to the control electrode of the device 52. rlhe control electrode of the device 52 is Valso connected through a resistor 56 to the negative terminal of a unidirectional source of potential. The anode of the device 5| is connected through a load resistor 51 to the positive terminalv of a unidirectional source of potential, illustrated 'by the symbol B+. VThe values of resistorsv 55, 56 andV 51 Vare soV chosen that the controlfelectrode of devicev 52 v'normally -holds that device'in a conductive state.l Device 52' thus'furnishes sufficient ,biasl across `resistor 53 to cause the device 5| normally to be held ina non-conductive condition. The positive going portion of the ampliiied input wave, which is supplied to the electrode of device 5|, causes the device 5| to conduct and due to thecommon cathode connection offthe two devices there is'an abrupt change, or switchingaction, in `which tlie device 52 is' turned oi and the device! 15 |"turne'd onl.- lThe capacitor 51|, 'which ijs preferably .oirela-i tively small capacitmoperate's to lay-pass: there sisto'r'55athignirequencies softhat the switching action takes; place in' ,avery yshort period of time and! thereis produced-in the anode circuit ofthe device 52 a' recta'ngular'shaped wave having'rela-l tively steep'Sl'oped-leading and trailing edges'- and' having a'frequency equaltot'hatof the income i'lgv'WaVe." .i v v n In ldei" 'to' establish phaS'bOiI'lCideCe betwell the rectangular wave produced at the voutput tei"- 'minals or" the" squaring circuit I3 and the desired pO'ItiI'i' 0f the'ilpl'lbwave, l'lhly iS provided mahs for' adjusting the' phase of the produced rectang'u lar Wave with respect lto the sinusoidal input wave. In the illustrated embodiment, ableeder network is provided for this purpose which comprises a resistor 66 and a -potentiometer`- 5|. These circuit elements are connected in series-be; tween the positive and negative sources of poten# tial. 'The arm ofthe potentiometer is connected through a pair of resistors r|52 and 63 tol thecon trol electrode of the device 5|. With 'this arlrangement, the Aiixed bias on the control electrode of the device 5| may be varied so as to'vary the point in the cyclev of the amplified input wavjat which switching of the devices 5| and 52-occu`rsi To provide control pulses which coincidefwith the 4leading and trailing edges of the' rectangular output from' the squaring circuit i3, there pro-jvided means for diierentiatin'g the rectangular wave to obtain sharp lcontrol pulses, successive vones of which are of opposite' polarity. Speciiiu cally, the differentiation of the rectangular Wave is accomplished by means of a differentiating cir cuit which includes a capacitor 65 and theftotal impedance from the right hand side of the capacitor 65 to ground. This total impedance includes the common anode resistor for thetubes 61 and`-68 in parallel with the series combinations loi' the resistors 66 and 'l2 and the tube resstances. respectively associated therewith to ground.

While the gating pulse trigger circuit lmay comprise any suitable circuit arrangement for producing'gating pulses in response to the differentiated control pulses, I prefer to employ 'a iiip` flop circuit, commonly known as an Eccles 1 Jordan trigger circuit, this circuit being modied in a manner to be described hereinafter'to provide proper operation with the biasingy trigger circuit. In the specific embodiment illustrated iin Fig. 2, the modied Eccles-Jordan circuit'comprises a pair of electron discharge devices 61, 68v

the cathodes of which are connected through-a common cathode resistor 59 to ground potential. The ranode rof each of the devices 61 andB'Bis cross-connected through a conventional RC network to the control electrode of the opposit'edev ment, the gating pulse trigger circuit is turned on and oit by vsuccessive negative 'pulses and the circuit is not responsive to-'contro1 pulsesof'posie 7 tive polarity. Thus, positive control pulses suppliedzfromthe diierentiating circuit to the anode of device 61 are coupled to the control electrode of device 68, but produce nochange there` in inasmuch as this device is normally conducting; The positive control pulses supplied tojthe anode of the device 68 through its load resistor 12 are also supplied through the RC network 13 to the control electrode ofthe device 61. YHowever, the device 61 is normally held non-conductive by an amount sufficient to prevent conduction thereof in response to the positive control pulses.

Inasmuch as the devices of the trigger circuit I are simultaneously switched from a conductive to a non-conductive condition, there is produced in the anode circuit of these devices gating pulses of opposite polarity, the leading and trailing edges of these pulses coinciding respectively in time with a iirst, active, negative control pulse and the next succeeding negative control` pulse. These Oppositely sensed gating pulses are directly impressed through isolating resistors 15, 16 upon the clipper-amplifier circuit I6 wherein they are squared up so asto decrease the leading and trailing edge intervals thereof and equalize the same so as to reduce switching transients produced in the balanced gating circuit I1. VThe isolating resistors 15, 16 are connected to the control electrodes of a pair of electron discharge devices 11, 18. The control electrodes of the devices 11, 18 are also connected through grid bias resistors 19, 80 to a negative source of unidirectionalv potential. The devices 11, `18 are utilized to provide amplification for the oppositely sensed gating pulses from the trigger circuit I5. Due to the fact that the control electrode circuits of devices 11, 18 are operated at a substantial negative potential the gating pulses are clipped off so as to provide in the anode circuits of devices 11, 18 gating Apulses which are of substantially steeper slope and more uniform amplitude than those originally produced in the anode circuits of circuit I5.

The clipper amplifier I6 has the important additional function of removing the positive control pulses which are superimposed on the gating pulses produced by the gatingpulse trigger circuit I5. In this connection, it will be recalled that while the positive pulses from differentiator I4 do not actuate the trigger circuit I5, they nevertheless pass through the circuit I5 to the input circuit of the clipper amplifier I6. This is readily apparent when it is realized that those positive pulses are supplied to the anode circuits of devices 61 and 68 through the resistors A66 and 12 and thence to the input circuits of the devices 11 and 18 regardless of the operation of trigger circuit. I5.v However, the undesired positive pulses are removed in the clipper amplifier I6 so that symmetrical gating pulses in amplified form are provided in the output circuit of clipper ampliiier IB. With regard to the clipping action of the circuit I6, it rwill be understood that the undesired positive pulse superimposed on the positively sensed gating pulse supplied to device 18 is ineffective to change thecurrent in the anode circuit of "device 18 inasmuch as the device 18 is already drawing maximum .current Hence the superimposed pulse does not appearv inthe anode circuit of device 18. The undesired positive pulse supplied to device 11 is removed by grid clipping in the opposite direction as will be readily apparent to those skilled in the art.

The steep sided gating pulses produced in the anode circuits of the clipper-ampliiier are supplied to the balanced gate circuit I1 to control selection of the desired portion of the periodic input wave. Thus these pulses are directly suppliedfrom the anodes of the devices 11 and 18 through the isolating resistors 85, 86 to the control electrodes of electron discharge devices 81. 88. The cathodes of the devices 81, 88 are connected through a common cathode resistor 89 to ground. The control electrodes of the devices 81, 88 are connected through grid biasing resistors 90, 9| to a negative source of unidirectional potential. Isolating resistors 85, 86 and grid bias resistors 90, 9| are all preferably `of the same value so as to allow introduction of the gating pulses to the control electrode circuits cf the devices 81, 88 without interacting with other sources connected thereto.A Inasmuch as gating pulses are supplied to the control electrodes of devices 81 and 88, these devices are simultaneously switched from a conductive to a non-conductive condition in response to the gating pulses.

The 4ampliiied input wave developed in the anode circuit of the input amplifier I2 is applied through an isolating resistor 92 to the control electrode of the device 81. The isolating resistor 92 preferably has a value similar to that of isolating resistors and 88 so as to preserve the bias conditions on the devices 81, 88 of the balanced gating circuit and to prevent interaction between the interconnected circuits. Inasmuch as the device 81 conducts only for the time duration of the gating pulse supplied thereto, there is produced across the common cathode resistor 88 only that portion of the continuous input wave which occurs during the gating interval.

If the tubes 81 and 88 draw equal currents through the common cathode resistor 89, substantially no voltage variations will be produced across the common cathode resistor as a result of tube switching inasmuch as the voltage produced across the resistor 89 due to the flow of current through either tube will remain the same. In order to prevent the gating pulses from appearing across the common cathode output resistor, means are provided for equalizing the currents drawn by the devices 81 and 88. In the circuit of Fig. 2, such means comprise a ypoten tiometer 93 connected in series between the anode and control electrode of device 88. Inasmuch as the potentiometer 93 is connected to a positive source of potential through a common decoupling resistor for the tubes 81 and 88, the current drawn by device 88 when that device is in a conductive state may be varied by adjusting the potentiometer 93. With this arrangement, the base line of the signal produced across resistor 89 remains substantially undisturbed during the interval between gating cycles and the gating pulses themselves do not appear across the output resistor 89. The test signal produced across the output of balanced gate circuit I1 is applied through a capacitor 94 to acontact 85 of the selector switch II. When this switch is .in its uppermost position, the test signal is applied through the arm 96, a resistor 91 and the potentiometer 98 -to the control electrode of an electron discharge device 99.

In the ideal situation, the test signal would comprise a straight time base line broken only for the duration of the superimposed single cycle of the incoming wave. However, during the leading and trailing edge intervals of the gating pulses supplied to fthebalanc'edgate circuitxll, small transient voltagesare produced across the common cathode resistor dueto lack ,of exact symmetry in thefrise-andfall'of the gating pulses applied to the two control electrodes. of theicircuit. To remove switchingl transients which may appear across the cathode resistorzBB, a'multisection filter circuit is Vprovided the, individual sections of which provide progressively greater filtering action. Any particular Isection' may be selectively employed to filter .out the relatively high frequencies' which make up; the switching transients. In the .illustrated"embodiment, the filter circuit is indicatedas an integration;cir cuit comprising a resistor 9'1 and af. plurality of capacitors 100. -The capacitors `100,.whichmay vary in capacity from a valuefof 100 micromicrofarads to 'a value of 3,000 micromicrofarads are selectively connected across the potentiometers by means of step switch indicated generally at 101,. With this arrangement the filter section may be selected whichrminimizes the switching transients while producing a minimum of roundingV off vofjthey selected sine wave.;` In `this. connection, .it will be understood that selection of too large a capacitor produces too muchA integration andr hence the high rfrequency components contained in the abrupt change from base; line to sinusoidal wave are removed and the; end portions of the selected cyclefareirounded of.

Byfproviding the described.' conductive or D C. coupling between-the gating pulse triggerv circuit 15, theclipper amplifier circuit 16 and thebalanced gate circuit I'1low frequency. phenomena, in thegorder of cycles ,per second, may be suppliedto the-electronicwave chopping circuit and maybe utilized to control 'the gating pulse trigger circuit. Also, the provision of direct coupling between the'f'above described circuits eliminates any time constants whichfwould tend to charge up and round 01T the sharp leading and trailing edges `of 'the gating pulses. By providing .steep sloped gating pulses, the switching transients which arise during the gating operation due to imperfect symmetry between 4the oppositely sensed pulses are of relatively .high frequency. AS a consequence, theswitching transients which are of relatively high frequency canbe removed, by'ltering action, from a relatively low frequency input wave without materially affecting the. selected portion of the input wave. The vtest signal, which comprises a single selected cycle of the continuous wave is thus supplied to the control electrode of amplifying device 99 wherein it is amplified and supplied through a coupling capacitorv 105 tothe control electrode of a pentode type electron discharge device 106'; To' effect linear amplification through the devices 105 and it, and also to provide increased arnplication for a low frequency input wave, there is. vprovided a feed back network from the anode ofthe device 106 to the input circuit of the device 99. Specifically, the feedback circuit comprises a capacitor 101 and resistor 108, which vare connected in series from the' anode of the device 106 tothe ,cathode of the device 99, and an unbypassed vcathode resistor 109 Vconnected 'between the-cathode of device 99 and ground. With this arrangement, amplied signals appearing inthe anode circuit of the device |06 are fed back to the cathode circuit of the device 99 in such phase as to oppose changesk in the input voltage. This degenerative feed back voltage stabilizes the final Vamplifier circuit and provides linear amplifications at relatively low frequencies, as will be 1o readily apparent to those skilled in the art. The

device V|06 is also provided with` anunby-passed Y cathode resistor 110 in order further to linearize theamplification'. therein. The .amplified test.

continuous wave is to be selected, there is proy vided a biasing trigger circuit which controls the gatingfpulse trigger circuit in such a manner that-the circuit is disabled except during periods when the biasing trigger circuit is turned on. More specically, the 'biasing trigger circuit comprises.a. pair of electron discharge devices Hiandll'l the `cathodes Vof which are connected to'ground-.and the anode circuits of which `arc cross connectedv through RC networks 117, fllil` to the'controlelectrodes of the opposite devices 'The control electrodes of the devices i115, 1 16' are connected through grid lbias resistors 119, 1Z0-tc' the negative terminal of' a unidirectional source of. potential. The anode of the device |15 is connected through a variable resistor '121 tov the normally nonconducting device 61 of the gating pulse trigger circuit I5. The bias voltage for the device 5i is thus determined in part by the bleeder networkV comprising resistors '11, '12 and 13 and is also determinedby the'variable resistor 121v and the anodeload resistor 122 of the device |15.- Thus when the device 11S-is in a conductive state, that is, when the biasing trigger circuit is in its so-called turned off condition, the flow` of anode current through thev resistor 122 produces apotential drop thereacross so that the anode of device 15 and correspondingly the control electrode of: device 61 is at a negative potential, thus increasing the'bias voltage which must be overcome to control the gating pulse trigger circuit. j To turn on the biasing trigger circuit, there is provided a starting circuit, which maybe closed bythe operator of the device, and which supplies a positive voltage to the control electrode of the device 116. Closure of the switch circuit di' thus causes the device 115 to be placed in a conductive state with the result that the device is rendered non-conductive.y When the devicer 115 is rendered non-conductive the anode voltage thereof rises, causing the bias voltage at the control electrode of the gating pulse'trigger circuit torise. by a proportional amount. Thus, actuation of. the manual start switch 21 produces a biasvoltage change whichfconditions the ,circuit 15 for control by the control pulses supplied thereto. .The amplitude of the bias voltage supplied by the biasing circuit 23 may be varied by adjusting the resistor 121 to a point where the control electrode bias on device 6l is too great to allow conduction .of that device.` The negativev control pulse immediately following the leading edge of the step bias wave produced by the biasing circuit thus operates to turn off the idevice S8 and, throughthe network '13, simultaneous to turn on the device 61. The next succeeding control pulse causes a corresponding switching on and off of the devices 61 and-58, device 68 being switched to a conductive state.

In order'to .turnfoii' theibiasing trigger circuit at the end-oftheproduced gating pulses .so that a single icycleof thetcontinuo'us wave is selected, there is provided av feedback circuit from device 68 vto device H0. Specifically, the feedback circuit comprisesa capacitor |24 connected from the anode of 'device' 68 to the control=electrode of device IS through the switch 25'. 'The capacitor |24 is preferably of small value so as to differentiate Vthe gating pulse appearing at the anode of the device 68. Differentiation of the gating pulse at the anode of device 68 produces a negative pulse coincident with the trailing edge of the'gating pulse, which negative pulse is operative to turn oi the biasing trigger circuit. For single cycle operation, the biasingr trigger circuit then remains in a disabled state until subsequent actuation of the manual start switch 21, whereupon the enabling and disabling cycle discussed above is repeated.

In thevevent that a particular nth cycle of the continuous wave is to be selected there is provided a variable frequency oscillator, lwhich may be utilized in place of tliemanual starting switch 21 to turn on the biasing trigger circuit 23 and thus condition the gating pulse trigger circuit for controlled operation. Specifically, the variable frequency oscillator comprises a gaseous discharge device |25, the anode of which is connected through a variable resistor |26 and fixed resistor |21 'to the positive terminal of a unidirectional source of potential. The anode of device |25 is also connected through a selector switch |28 and capacitor |29 to ground potential. Additional capacitors |30 of various valuesmay be selected by the switch |28 to provide various operating frequencies for the oscillator. The cathode of the device |25 is connected through an output resistor |3| to ground potential and is also connected through the resistor |32 to -I-B potential. The oscillator described above comprises a conventional gas tube relaxation oscillator wherein the particular selected capacitor |39 is charged through resistors |20 and |21 towards the positive unidirectional source of potential. When the voltage across the capacitor exceeds the breakdown potential of the gaseous discharge device |25, the device conducts and rapidly discharges the capacitor to a point of sufficiently low potential that the arc discharge between the cathode and anode of the device |25 can no longer be supported. Conduction in device' |25 is thus halted and the cycle is repeated. At the instant' of conduction of the device |25, there is produced across the cathode resistor |3| apositive pulse, due to the iiow of cathode current therethrough (which positive pulse is con. nected through the selector switch 29 and coupling network |32 to the controlelectrode of device ||6. The positive pulses appearing across the resistor |3| at the operating rate of the variable frequency oscillator thus operate to turn on the biasing trigger circuit in a manner similar to that produced by manual actuation of the starting switch 21. The biasing trigger circuit is again turned 01T by means of the feedback capacitor |24 in the manner described in connec- -tion with the selection of a single cycle of the incoming Wave.

In order to synchronize the variable frequency oscillator with the incoming continuous wave so that the same fixed portion of the continuous Wave may be selected, there is provided a coupling resistor |35 which is connected from the anode of device 45 to the control electrode of gaseous discharge device |25, Athe control electrode being connectedv to'ground through a grid leak resistor |36. With this arrangement, the posif tive portions of the. amplified continuous wave appearing at the anode of the device 45 are utilized'to controltheiiring of device |25 and hence the timing of the positive control pulses which. appear across the cathode resistor 3|. Relatively large changes in the frequency of the oscillator may be obtained' by selecting various ones of the discharge capacitors |30 associated with the anode circuit of device 25, it being understood that the inputlwave pulls the oscillatorzinto synchronism therewith so that the oscillator'frequencyvariesin steps rather than continuously.' Adjustment of the frequency of the oscillator in .between the steps afforded by capacitors |30 is provided by variation of the charging resistor |26 which operates to vary the charging rate of the particular selected capacitor and hence the time at which the gaseous device |25b'reaks down. It will be understood that the incoming wave supplied to the control electrode of the device |25 continuously synchronizes the oscillator, although the frequency of the voscillator may be varied over a relatively widerange inasmuch as the oscillator is operated at a frequency substantially below that of rthe continuous wave supplied to the input terminals of the circuit.

To provide for the introduction of auxiliary signals, such as chopped speech, or the like, during the chopped out portions of the continuous wave, thev balanced gate circuit l1 is provided with an input circuit comprising an input terminal |40, a Acoupling capacitor |4| and an isolating. resistor |42 which are connected in series tothe control electrode of device 88. In this connection .it/willbe understoodthat the amplified input Waveis supplied to the control electrode of the'device 81 and a portion or portions of the wave are passed to the common cathode circuit 89 depending upon the particular operation of the gating pulse trigger circuit and the biasing trigger circuit. By providing the auxiliary input circuit discussed above, other'signals, such as noise voltages or a speech wave train, may be supplied to the gating,V circuit in such a manner that the portion of the auxiliary signal which occurs between the selected cycles of the incoming wave 4I0 are mixed with the selected cycles of the incoming wave in the cathode circuit 89 and supplied through the iinal amplifier and iilter 20 to the equipment under test. Such an arrangement is particularly suitable for use in checking the operation of the equipment when subjected to chopped speech. In such case, the speech Wave train is connected directly to the auxiliary terminal |40 and portions of the speech wave train which occur between the selected cycles of the sinusoidal wave |0 are also supplied to theiequipment.

In order to visualize more clearly the operation of the above-described system and the particular wave forms produced therein, reference is now had to Figs. 4(a)4 d) wherein there are illustrated timing diagrams of particular portions of the circuit of Fig. 2. In Fig. 4(a) there is illustrated the timing wave forms which are produced `in the circuit of Fig. 2 when the selector switches 25 and 21 are closed, that is, the operation which obtains when a single cycle of the continuous wave is selected. Referring to'Fig. 1(a), there is illustrated in timing diagram .I several cycles-of the sinusoidal input wave ITE. Timing diagram II shows the rectangular shaped output wave |45 produced in the output of the squaring circuit |31, the leading and trailing edges |46 of the wave |45 being illustrated as occurring at the zero, or crossover, points of the sinusoidal wave l0. Timing diagram III illustrates the output. of the diierentiating circut I4 and comprises positive control pulses |41, which are derived from the leading edges of the rectangular wave |45. and negative control pulses M8 which are derived from the trailing edges of the wave |45.

In timing diagram IV oi Fig. 4m), there is shown the positive control pulse 49 which is produced upon actuation of starting switch 21. In this connection it will be understood that the pulse M9 may occur at any time as it is dependent upon manual actuation of switch 21. The positive control pulse Hi8 initiates astep function bias wave |56 which is produced by the biasingV trigger circuit V23 and which is illustrated in timing diagram VI. The amplitude of the biasl wave 59 is made suicient to condition the gating` pulse trigger circuit for control by the next succeeding negative controlv pulse of timing :diagram III. The gating pulse trigger circuit is turned onrby the first negative control pulse which occurs after initiation of the bias-wave |59, that is, the negative control pulse |48- of timing diagram III. Thev gating pulse trigger circuit is turned off by the next succeeding negative control pulse so as vto provide a positive gating pulse and a negative' gating pulse |52 as illustrated in timing. diagrams VII and VIII, respectively. With the selector switch in a closed position the trailing edge of the gating pulse |5| is diiierentiated by capacitor |24- to produce a negative feedback pulse |53', illustratedV in timing diagram V. The feedback pulse |53 turns off the biasing trigger circuit thus causing termination of the step function bias wave |50 illustrated immediately therebelow in timing diagram VI.

' As illustrated in diagrams VII and VIII, the corners of the gating pulses |5| and |52 are considerably rounded oli due to the capacity associated with the anode circuits of the gating pulse trigger circuits. Also, pulses |54 corresponding to the positive control pulses |41, pass through the gating pulse trigger circuit and appear superimposed upon the central portion of the gating pulses |5| and |52. However, the clipper ampliiier I6 operates to sharpen the leading and trailing edges of the pulses |\5| and |52 and also to remove the undesired positive pulses |54 as has vbeen discussed in detail heretofore. The gating pulses from the output circuit of the clipper amplifier i6 thus appear as oppositely sensed rectangular pulses |55, |56, shown respectively in Vtiming diagrams IX and X which gating pulses are substantially mirror images of one another Y so as to provide relatively small switching transients in the balanced gate circuit The selected' portion of the input wave I0 which occurs during the gating interval of pulses |55, |56 is illustratedrin timing diagram XI as thefsingle cycle |51 of the sinusoidal inputwave l0.

vIn order properly to understand the operation of the step switch iilter circuit of Fig. 2 inremoving the unavoidable switching transients producing during the gating of the continuous wave, reference is now had to Fig. Md) wherein a representative test signal is illustrated in more de- 14 tail. In Fig. 4&1) Hthe singleselectedcyclef-"I is illustrated as having a peaktopeak amplitude A; .The switching transients which occunduring thev leading and trailing edge intervals of the gating pulses are at |10 and respectively; The peak to peak amplitude of the. undesired switching transients |10, `isshown at-tiin Fig. Md). Thepercent of extraneoustransients produced in the test signal` is thus equal to? Y? l To utilize. the test. signaly |51v in analyzingtl/jle transient response ora yparticular equipment it is necessary to reduceth'e extraneous transients produced by the gatingcircuit `I'l toaQvaluecQn-f siderably smaller than thatwhichcan bedetected by a conventional oscilloscope connectedtothe output ofthe equipment being tested.. Otherwise, the operator cannot evaluate ,the response of theequipment under test as he cannotse'pagrate the.A transient .response lof the. equipment under test' Afrom the Ytransients .already existing in the test signal supplied thereto.. I In.v actual practice, it'has been found that a reduction .of the extraneous transients ,in the test signal "to about V3 per .cent of the' peakfto peak -amplitude of the test signal is .satisfactory to. permit use ofthe test signal in analyzing transient response, Therefore, to obtain the necessary-reduction'in extraneous transients,- the 10Wy .Pass lter circuit of Fig..2. is, employed. AThe amount of highirequency attenuation, and .hence reductionof, fthe relatively highfrequency transientsis dependent upon.y the particular. rvsection ofv theqlterggem: ployed. 'If toolargea capacitor I .UUQIFigL 127)'i`s` utilized the corners. at vthefbeginningv andfend ofthe selected Vcycleare roundedoffas illustrated by the dotted line [12in Fig. 40d) ,Q11 thepthl hand, if too.` little iilteringis used thesw'itching transientsl are still vdetectable. von anoscilloscope.V -`Optimum'filtering exists ata point inter-f mediate the extreme conditions `of. excessive roundingv oi, 'as' at |12 and excessive transients as Yat Il in Fig. 4M), and may beiobtainedfby selective adjustment of the filter network'.

InFig. 4(1)) .there is illustratedthe'timillg wave forms which occur in the electronic lwav", "chopping circuit of Fig. l whenthevariablefre ency oscillator 28 isemployed tocont'rol thebiasing trigger circuit 23. For such operation 'the switches 25 -and, 29 are closedand the vswitchf2`| is opened..` In Fig. 4(0) the same ref erence'numerals asl shown in Fig. 4m.) are' employedto identify the timing waveforms associated with the various portionsl of" the circuit. p' In, 4(1)), the continuous wave suppliedjto the input circuit of the equipment is shown asa sinusoidal wave l0, there being' a greater number: of* cycles thereof illustrated'toj' indicate the selection' of every nth cyclethereof. inasmuch as the oscillator I23 is operatedat a lower frequencythanithe incoming wave,- startingpulses |49, illustrated in timing diagram IV, occur-'at a :substantially lowerfrequency than the differentiated V( :ontrol pulses |41, |48 and in synchronism therewith".

With the set of conditions illustrated in 4(6) ,the oscillator, whichV produces the positive starting pulses |49 suppliedto the biasing'tri'g'- Vger circuit, is operated at one-third the-frequency of-the continuous input wave I0 vso thatevery third cycle ofthe continuous wave *isv produced in the output circuit of the iinal ampliiier', as illustrated in timing diagram` XI. It is evident that -the positive pulses v|54,*whch are again passed by thev gating pulse Vtrigger circuit, .are

removediin the clipper amplifier circuit so that a faithful reproduction of selected single cycles ofv the continuous wave is obtained in the outiit circuit of the electronic wave chopping sysxn.k In theevent that alternate cycles of the continuous waves are to be selected in the output circuit of the wave chopping system the operation illustrated in Fig. 4(c) may be provided. Such operation obtains when switch 21 is closed to initiate a step function of bias Voltage, switches 25V and 29 being open for this type of operation. DueV to the fact that feedback connection 'from the gating pulse trigger circuit to the' bias trigger circuit is vopened for alternate cycle'operation, the bias voltage from the biasing triggl circuit remains at maximum amplitude as illustrated at |15, and hence the gating pulse trigger' circuit continues to be turned on and oif byfsuccesslive negative control pulses |48 so that gating. pulses |55, |56, occurring at one-half the frequency of the continuous input wave, are supplied to the balanced gate circuit |1.=

In the event that the electronic wave chopping circuit is to be utilized for other applications, as., for example, to compare portions of two or more waves to obtain the frequency response of electrical equipment to both of such waves, modification of the balanced gating ,circuit |1 may be made in the manner illustrated in Fig. 3.` In

Fig. 3 certain elements of the'balanced circuit discussed in connection with Fig. 2 remain the same and a detailed description thereof is considered unnecessary herein. For` purposes of clarification, identical reference numerals for circuit elements common to both Figs. 2 and 3 have been employed. In Fig. 3 the gating pulses from the clipper amplifier circuit are again supplied through isolating resistors 85, 8| l to the control electrodes of the devices 81, 88. The input wave from amplier l2 (Fig. 1) is illustrated as being connected to the control electrode of device 81 througha resistor 92 and -a selector switch |60. In addition to the auxiliary input circuit Vassociated with the control electrode 'ofdevice 88, there is provided in Fig. 3 a second auxiliaryinput circuit comprising an input terminal 62, coupling capacitor |63 and anisolating resistor |64, which elements are connected in series to the control electrode of device l 81 y In the event that the input wave fromrthe ampliiier |0 is not supplied to the control electrode of'device 81, the switch |60 is utilized to connect a variable balancing resistor |6| from a positive source of potential to the control electrode of device 81. When the resistor 02 is removedV the D. C. balance of the gating circuit is upset due to the fact that the resistor 92 is directly connected to the positive source of potential through the anode load impedance of device 45. However, the resistor |6| may be varied to rebalance the gating circuit |1 so that the -devices 81, 88 thereof draw equal currents when in a conductive state.

N'When the modiiied gating circuit shown in Fig. 3 is employed in the electronic wave chopping circuitof Fig. 2, a versatile circuit is provided wherein a wide variety of dierent test signals may be obtained. For example, a first auxiliary signal may be supplied to the iirst auxiliary input terminal |40 and a second auxiliary signal may be supplied to the second auxiliary input terminal |62 and the wave from input amplier |2 removed from device 81. The auxiliary signals may comprise any arbitrary waveform having no phase relationship to the incomingwave |0 which controls the gating circuit. With the selector switches 25 and 21 (of Fig. 2) open, and the variable oscillator switch 29 closed a xed portion of the auxiliary signal supplied to the terminal |62 is intermixed with a variable portion of the auxiliary signal supplied to the terminal |40, the intermixed selected portions appearing across output resistor 89. By such an arrangement a simulated multiplexing signal is provided whereby the equipment under test may be analyzed for simultaneous response to chopped portions of two independent wave trains. It will be understood that the above example of the type of test signal obtainable from the electronic wave chopping circuit is given only by way of illustration, and that many other types of test signals may be obtained as will be readily apparent to those skilled in the art.

While the electronic wave chopping circuit of Fig. 2 is specifically arranged to select particular portions of a continuous wave of relatively low frequency, it will be understood that the frequency range of the' wave chopping circuit of Fig. 2 may be substantially increased. For example, pentode type electron discharge devices may be utilized in place of the triode devices shown in Fig. 2 for the gating pulse trigger circuit, clipper amplier circuit and the balanced gate circuit. By employing pentode type devices having relatively high gain, the switching transients occuring during the leading and trailing edges of the gating pulses are of substantially higher frequencyy and may be removed by relatively slight filtering action thus permitting the use of a relatively high frequency input wave.

While there have been described what are at present considered to be the preferred embodiments of the invention, it will be understood that various modications may be made therein which are within the true spirit and scope of the invention as defined in the appended claims.

I claim:

l. An electronic Wave chopper comprising, a periodic wave source, means for deriving from said source a gating pulse having a time duration equal to a predetermined discrete time interval of said periodic wave, and signal transmission gating means controlled by said gating pulse for selecting a predetermined'portion of said periodic wave. A

2. An electronic wave chopper comprising, a periodic wave source, means for deriving from said source apair of gating pulses of opposite senses and of a time duration equal to one cycle of said periodic wave, and signal transmission gating means controlled by said oppositely sensed gating pulses to gate one or more signals during the persistence interval of said gating pulses.

3. An" electronic wave chopper comprising, a periodic wave source, a normally closed gate circuit adapted when open to transmit therethrough a periodic Wave from said source, means forderiving from said source control pulses indicativev of a predetermined discrete timeinterval of said periodic wave, and means controlled# by said control pulses for opening said gate circuit during said time interval, thereby to selecta predetermined portion of said periodic wave.

4. An electronic wave chopper comprising. a Continuous periodic wave source, means for selectively deriving from said source pairs of oppositely sensed gating pulses having a time duration equal to one cycle of said periodic wave and l'7A having" a recur1ence -1ate--e'qualitol a-` sub multi-ple ofthe periodicity vofsaid periedi'c'wave, and-means controlled byV saidpairs of' oppositelysensed" gat'-r ing pulses forselect-ingthat portioni oi*- saidv vva-ve Which occurs during the persistenceintervall ofsaid gating pulses;

5. An electronic wavehopper comprising; a continuousv periodicMv/avesourcewmeansfor' deriving from-said source oppjositely-sensed-:gating pulses yhaving atime duration 'equal to one cycle of said periodic Wave, said last namedmeans-including selectively operable means mfor controlling the, timeof occurrenceofi-saidl gatingcpulsesy-andi means controlled-by said gating pulses-- for' selecting that portion of said wavevvhi'ch'cccurs during the persistence interval offsaid-'gating pulses.

6; An electronicr vva-vechopperr"comprisingz'ax continuous periodic'- WaveV source,meansffor'fde riving from said sourcecppositelyI sensed-:gating pulsesrhaving-a time v-duration'equalitoone cycle of `said` periodic-wave, selectively-operable means for controlling-said gating pulse; meanstodeterY mine the time -ofoccurrence' off-'saidL pulses.-v and means 'controlled-by" said? gating pulses4 forl select'- ing-that portion of said-XvvaveiWhichfoccurs--during the persistence 4intervalfCisa-id gating pulses. 1

7". An electronic-Wave chopper` comprising,L a-

periodic VWave source, trigger'circuitAv means# for deriving fromsaid sourcera pairj of-gating-pulses of opposite senses and? cfa time-duration" equal to koneA cycle' of said periodic Wave,` meansr` con..y trolled by nsaid pairci oppositely'sensedgating pulsesV for select-ingthat por-tion --or sa-i'di' Wave which Voccursv during'thei'persistencewiritervalA of said lgating pulses; andi@ mea-ns fcrshifting the phase of said gating pulsesrelativetolsaidiperiodic Wave', thereby to vary -theselectedlport'icn ofsaid Wave.

8. An electronic Wave=-clf1cpperfcomprising;` a periodic Wave source; triggercircuit meansy -for deriving from' said sourcea` pair` off-gating pulses of opposite sensesand-of-"a tirnevduraticn-equal' to onecycleof said pericdicwvave; means utilizing said` pair ofl oppositely fsensedl gating-I -pulses' for selectingthat por-tionA ci' said; Wave which* occurs duringV the time durationlfcfsaid- -gating- -pul'se's;'

andl 'filteringmeans yconnected to saidselecting means forn suppressing switching transientsivvhich occur during-'the leading-anditrailing-'edge inter: vals of said gatingy pulses-While' passing substantially, unchanged: the selected portion'i offsaid periodick vvave:v

9. An electroni'cfwavefchopper comprising-fa periodic Wave source, mean'sf for Vderivingfrom said source pairs' of oppcsitel'y;lsensed-1 gating pulses, each of said pulse'sicorres-pondingfin-'time to alternate cycles of saidperiodicwave andhaving a time durationV equal to--one-cf,fcle`^ thereof; andV means utilizing'said pairsofI-cppositely sensed pulses' for selecting',` those'pcrtionsof said periodicv Wavewhich occur@duringsaidtimeedurae ton.

10. An electronic vvave chopper comprising, a periodic Wave sourcegtrigger vcircuit"- means 'fior deriving from said; source pairs offoppositely sensed, gating' pulses,y -veaolr of-said vpulses ycorresponding in time Ato alternaterfcyclesoff-said periodiowaverand Vhaving a; timer-duration equal tov one" cycle `thereofgmeans utilizingsaid* pairs of oppositely sensed: pulses '-for selecting those-:portions of said1 vperiodic .Waver which `occur during said time duration,` and mea-nstor-,sliifting-v the phase of said pairsY of/pulses relativeto-said periodic Wave thereby to control' the' starting pointofA the selected*v portions'ofI saidway 11. -Anelectronic wave chopper-fl comprising, -a periodic wave source, trigger circ-uit means for' deriving Afrom said; source -pa-irs of oppcs--i'lelyl sensed gatingpulsesi each; of said pulses ccrrespending -i-n time to alternate cycles-ofsaid periodio Avvave and having a time duration equal to one Acycle thereof', means utilizing said? pairs of opposit'ely sensed-pulses for selecting those portions-of said periodic Wavevvlf-iichl occurdur-ing said time duration, and; filtering means-connectedto said selecting'means-for suppressingswitching transients Which occur duringr the -leadingf andtrailing edge interva-lsof saidgating pulses While passing substantially unchanged the selectedI por*- tion of said periodic Wave;

l2; Anelectronic wave chopper comprising, a source ofVv periodic voltage;` means-'forl deriving. from `said source contrllpulses-of- -a-v given polarityand4 of the same-frequency 4as `said periodic volt'- age; a trigger4 circuit arranged-to be* turnedon by ya first one" of'4 said` control pulses andi turned offcby lthe next"succeedingy control pulse; means for derivingf-rom-said trigger circuit a pair ofgating pulses ot'opposite senses, balanced gating meanscontrolled by said gating pulses-lenselectingthatpmftionV of saidperiodicrvoltagewhich occursv duringsaid gating pulses,- andmeans'- for integrating the output' of saidV balanced-` gating means thereby substantially to reduce switching transients "Which Occur -duringthe leading;- and trailing edge intervals of said gating pulses- 132' An electronic'Wave"chopper-comprising a source orV :periodic voltage;- means-for deriving from said source control pulses of a givenpolar-ity and' of thesameA frequency as--saidperiodic voltage,a trigger circuit' arranged-to be--turned--on by a rst o ne'oiv said; control -pulses'andi turned oli` by Ythe next succeeding control pulse, vmeans for deriving from said` trigger-circuit a pairof gatingrpulses of` opposite senses; balanced gating means controlled-by' said gating pulses-y for selecting that portion of vsaid periodic voltage-which occursv during saidl gating pulses; and means-for shifting the phase of saidcontrol pulses relative to said periodic voltage to-seleeta` predetermined portion-of said periodic voltage.

14.- An electronic-Wave choppercomprising, a periodic wavesource,` means for deriving. from saidsource control pulses of a given-polarity and of -a frequencyr equal to -said periodic` wave, a trigger Vcircuit 'arranged to be turned? on4 byaf'rst one-ofV said control pulses and turned oft byfthe next succeeding control pulse, arelaxationoscillator arranged-toprovide` an output-Wave ofsub.- stantially-lowen frequency than said Wave and in synchronism therewith, means utilizing saidfoutput Wave iordisablingsaidtrigger circuit ,for a predeterminedinumber of-successive cyclesloisaid periodic Wave, means-for deriving f-romxsaid trig-` ger-'circuit pair-slof oppositelysensedgatingipulses having a tiinedurationequalltofone-cyole oi said periodic Wave and having-a frequency-of occurrenceequal Vte lsaid output -vvavet andi balanced gating means-1 controlled byssaid'. gating pulses-:for selecting those. portions oi' saidperodici'wave Which-occur during saidltime duration.. l

15.-' -Anelectronici AWav-eL chopper'.v comprising-1 a periodic wave source; means; yfori:deriving-fi' from sai-df source control pulsesr of. 1a.. given polarity-fand of 1 -afrequency equal' to, Saidf. periodici -Wave 4 .a triggerlcircuit varranged' to, be turnediom by larst one 'off said control `pulsesrand.` .turned `oizloythe next succeeding controla pulse; al. relaxation; osol:V later ar-ranged to provide' an loutputzwave'ofsube f stantially lower '-frequencyzthan.: said. .Wave land in synchronism therewith, means utilizing said output Wave for disabling said trigger circuit for a predetermined number of successive cycles of said periodic wave, means for deriving from said trigger circuit pairs of oppositely sensed gating pulses having a time duration equal to one cycle of said periodic wave and having a frequency of occurrence equal to said output Wave, balanced gating means controlled by said gating pulses for selecting those portions of said periodic wave which occur during said time duration, and means for shifting the phase of said control pulses relative to said periodic Wave thereby to vary the portions of said periodic wave selected by said balanced gating means.

16. An electronic wave chopper comprising, a periodic wave source, means for deriving from said source control pulses of a given polarity and of a frequency equal to said periodic Wave, a trigger circuit arranged to be turned on by a first one of said control pulses and turned off by the next succeeding control pulse, a relaxation oscillater arranged to provide an output Wave of substantially lower frequency than said Wave and in synchronism therewith, means utilizing said output wave for disabling said trigger circuit for a predetermined number of successive cycles of said periodic wave, means for deriving from said trigger circuit pairs of oppositely sensed gating pulses having a time duration equal to one cycle of said periodic wave and having a frequency of occurrence equal to said output Wave, balanced gating means controlled by said gating pulses for selecting those portions of said periodic wave which occur during said time duration, means for shifting the phase of said control pulses relative to said periodic wave thereby to vary the portions of said periodic Wave selected by said balanced gating means, and means for integrating the output of said balanced gating means to remove switching transients which occur during the leading and trailing edge intervals of said gating pulses without materially affecting the selected portions of said periodic wave.

17. An electronic Wave chopper, a periodic wave source, means for deriving from said source a pair of oppositely sensed gating pulses having a time duration equal to one cycle of said periodic wave and having a frequency equal to that of said periodic wave, and balanced gating means for selecting that portion of Said wave which occurs during said gating pulses, said last named means comprising a pair of electron discharge devices, a common impedance connecting the cathodes of said devices to ground, means for turning on and off said devices in accordance with said gating pulses, means connecting said periodic wave to one of said devices, means for equalizing the voltage developed across said impedance by each device during the turned on period thereof, and means for deriving from said impedance the selected portion of said wave.

18. An electronic wave chopper, a periodic wave source, means for deriving from said source a pair of oppositely sensed gating pulses having a time duration equal to one cycle of said periodic wave and having a frequency equal to that of said periodic wave, and balanced gating means for selecting that portion of said wave which occurs during said gating pulses, said last named means comprising a pair of electron discharge devices, a common impedance connecting the cathodes of said devices to ground, means for turning on and off said devices in accordance with said gating pulses, means connecting said periodic Wave to one of said devices, means for equalizing the voltage developed across said impedance by each device during the turned on period thereof, means for deriving from said impedance the selected portion of said wave, and variable integration means connected to the output of said balanced gating means for removing transients which occur during the leading and trailing edge intervals of said gating pulses Without materially affecting the selected portions of said periodic wave.

19. An electronic Wave chopper comprising, a periodic Wave source, means for deriving from said source a square wave having the same frequency as said periodic wave, means for shifting the phase of said square wave relative to said periodic Wave, means for differentiating said square wave to obtain control pulses of a given polarity, a gating pulse trigger circuit arranged to be turned on by a rst one of said control pulses and turned Aoi by the next succeeding controlpulse, manually responsive means for controlling the bias of said trigger circuit to condition said trigger circuit for actuation by said control pulses, means for deriving from said gating pulse trigger circuit a pair of oppositely sensed gating pulses, said gating pulses having a time duration equal to one cycle of said periodic wave, a feedback connection between said trigger circuit and said bias controlling means thereby to disable said bias controlling means at the end of said gating pulses, balanced gating means controlled by said gating pulses for selecting that portion of said periodic wave which occurs during said gating pulses, and variable integration means connected to the output of said balanced gating means for reducing transients which occur during the leading and trailing edge intervals of said gating pulses.

20. An electronic wave chopper comprising, a periodic wave source, means for deriving from said source a square wave of the same frequency as said periodic wave, means for shifting the phase of said square Wave relative to said periodic Wave, means for differentiating said square wave to obtain control pulses of a given polarity, a gating pulse trigger circuit arranged to be turned on by a first one of said control pulses and turned off by the next succeeding control pulse, a variable frequency oscillator operating at a frequency substantially lower than said periodic wave, means for synchronizing said oscillator with said periodic wave, a biasing trigger circuit arranged to provide bias voltage for said gating pulse trigger circuit to condition said gating pulse trigger circuit for actuation by said control pulses, means including a connection between said oscillator and said biasing trigger circuit for turning on said biasing trigger circuit, a feedback connection from said gating pulse trigger circuit to said biasing trigger circuit for turning olf said biasing trigger circuit, means for deriving from said gating pulse trigger circuit pairs of oppositely sensed gating pulses, said pulses having a time duration equal to one cycle of said periodic wave and having a frequency equal to the frequency of said oscillator, balanced gating means controlled by said gating pulses for selecting that portion of said periodic wave which occurs during said gating pulses, and variable integration means connected to the output of said balanced gating means for reducing transients which occur during the leading and trailing edge intervals of said gating pulses.

21. An electronic wave chopper comprising, a

21 periodic wave source, means for deriving from said source a square wave having the same frequency as said periodic Wave, means for shifting the phase of said square wave relative to said periodic wave, means for differentiating said square wave to obtain control pulses of a given polarity, a gating pulse trigger circuit arranged to be turned on by a first one of said control pulses and turned oi by the next succeeding control pulse, a biasing trigger circuit, means connecting the output of said biasing trigger circuit, to said gating pulse trigger circuit to condition said gating pulse trigger circuit for control by said control pulses when said biasing trigger circuit is turned on, manually responsive means for turning on said biasing trigger circuit, means for deriving from said gating pulse trigger circuit pairs of gating pulses of opposite senses, said pulses having a time duration equal 22 to one cycle of said periodic wave and having a frequency equal to one half the frequency of said wave, balanced vgating means controlled by said gating pulses for selecting those portions of said periodic wave which occur during said gating pulses, and variable integration means connected to the output of said balanced gating means for reducing transients which occur during the leading and trailing edge intervals of said gating pulses.

JOSEPH W. GRATIAN.

REFERENCES CITED UNITED STATES PATENTS Name Millerv et al.

Date Apr. 23, 1946 Number 

